Most foreign objects entering the eye are readily flushed out by the natural defensive mechanism of tears from the lacrimal glands. Those foreign objects which are not readily flushed by tears require other means of removal. When a foreign object either adheres to or becomes embedded in the corneal or conjunctival layer of the eye globe such that removal by flushing the eye with fluid is ineffective, removal by a mechanical device such as a very sharp disposable hypodermic needle or other rigid ophthalmological instrument is commonly employed. Among the problems associated with the use of mechanical instruments for removing foreign objects from the eye are (1) effectiveness of the instrument while avoiding undue physical damage to the tissue of the eye and (2) sterility of the instrument so that the chance of infection of the delicate corneal tissue is kept to a minimum.
The prior art has addressed these problems in a number of different ways which are either not as effective in removing foreign objects or considerably less safe methods than the present invention. U.S. Pat. Nos. 1,272,270; 1,263,942 and 1,305,442 show typical prior art instruments that depend on a flexible tip that must be moistened so that the foreign substance clings to the instrument and not the eye. None of these instruments are designed to effectively and safely get under an embedded foreign object to safely dislodge it from the delicate eye tissue. In fact, i.e. U.S. Pat. No. 1,305,442, one of these instruments consists of a rubber coated wire that is inserted in the eye which has the possibility of seriously damaging the eye if the wire breaks and comes through the soft rubber coating.
In U. K. Pat. No. 304,020 there is shown an instrument designed to get under the foreign object and dislodge it instead of having the foreign object removed because it adhered more strongly to the instrument than to the eye. This instrument consists of a pointed blade which is said to be effective in getting under the embedded foreign object by reason of loosening the embedded object with the blade and using a quill or feather on the other end of the instrument to sweep the object off the eye. The problem with this instrument is that because of its pointed blade design, it may easily puncture the eyeball by means of a misjudgment by the user as to the pressure that must be applied to dig under the foreign body sufficiently to safely lift and remove it from the eye.
A still further prior art instrument disclosed in U.S. Pat. No, 4,600,008 contemplates removal of a foreign body by means of a loop of thread that may be drawn over the surface of the eye underneath the eyelid to dislodge the foreign body but which is not abrasive enough to scratch the eye surface. If a foreign substance has adhered to the eye or become embedded in its tissue so that it cannot be removed by flushing the eye with a saline solution, a loop of the type suggested in this prior art device may not be sufficient to get under the foreign object and dislodge it regardless of the pressure that can be applied to the eyelid of a closed eye while the loop is being drawn over the surface tissue of the eye.